A close look at the methods used to measure and analyze PFAS emissions in the environment.

Per- and polyfluoroalkyl substances (PFAS) once hailed as industrial “miracle” chemicals, have since become a widespread environmental concern, with detections found in water, soil, air, and waste across the globe due to their resistance to degradation and their ability to migrate far from their sources. While early regulation focused solely on drinking water, PFAS are now being detected in complex waste streams, leachate, biosolid residuals, industrial emissions, and ambient air. These non-traditional matrices raise new questions about how to quantify PFAS. (note that different regulatory bodies and scientific organizations define PFAS compounds differently, using criteria such as molecular structure, chemical characteristics, and the degree of fluorination). As regulatory frameworks evolve and public scrutiny increases, industries and municipalities managing PFAS in waste and emissions face growing demands for reliable data. The methods used to measure PFAS in the environment must be fit for their purpose and produce accurate and defensible data suitable for the intended need.

Current PFAS Analytical Methods in Waste

The U.S. Environmental Protection Agency’s (EPA) regulatory framework for wastes such as wastewater, landfill leachate, and biosolids continues to evolve as our understanding of PFAS sources, fate, and transport expands. In January 2023, EPA announced its intent to develop effluent guidelines and pre-treatment standards for landfills that discharge leachate.¹ Since early PFAS regulatory efforts focused on drinking water, EPA first developed standardized methods for the analysis of PFAS in drinking water. Many laboratories modified their drinking water methods to analyze waste and solid samples as regulatory attention has shifted to other media. However, such modified analytical approaches were not standardized, which complicates interpretations and comparisons of data. To address these challenges, EPA has finalized two primary methods suitable for analysis of PFAS
in wastes, summarized below and in Table 1. In addition to the EPA methods for PFAS, other agencies (e.g., ASTM International, U.S. Department of Defense, and the International Organization for Standardization) have drafted similar methods for PFAS testing.

In January 2024, EPA finalized Method 1621² for the analysis of adsorbable organic fluorine (AOF) in aqueous matrices and Method 1633 for the analysis of 40 targeted PFAS in aqueous, solid, biosolid, and tissue media types. In December 2024, EPA published Method 1633, Revision A.³ Both methods are proposed for promulgation under the U.S. Clean Water Act through the Methods Update Rule 22 (MUR 22), which was signed by EPA on December 6, 2024. MUR 22 proposes to add these methods to 40 CFR Part 136, making them formally approved for regulatory compliance monitoring, including National Pollutant Discharge Elimination System (NPDES) permitting. While there are tens of thousands of potential PFAS, conventional testing methods like Method 1633A target only a small fraction of these chemicals. However, Method 1621 provides a bulk measurement of the AOF present in a sample for use as a proxy for total PFAS concentration.

Method ID	Method 1621	Method 1633A
Status	Final, Revision	Final, Revision
Purpose	Quantitative analysis for estimating total organic fluorine in aqueous samples	Quantitative analysis for 40 targeted PFAS in various media
Sample Media Types	Aqueous	Aqueous, solid, biosolids, tissues
Analytical Method	CIC	LC-MS/MS
Quantification Technique	External standard	Isotope dilution quantification
Reporting Limits (estimate)	5 μg F–/L	Aqueous Samples – 1-100 ng/L Solid Samples – 0.16-10 ng/g Tissue Samples – 0.4-20 ng/g
Quality Control	Robust QC includes instrument standards, spikes, and blanks.	Robust QC includes instrument standards, spikes, blanks, surrogates, and other QC check standards
Potential Interferences	High chloride concentration, high organic carbon content, non-PFAS organofluorines, cross-contamination	Bile salts; PFAS cross contamination
Limitations	Potential low bias due to challenges with short-chain PFAS; potential high bias due to non-PFAS organofluorines	Target list includes only 40; expensive; technically complex method requiring experienced analysts
Challenges	Potential elevated chloride, non-PFAS organofluorine, and other non-target interferences; PFAS and fluorine cross-contamination; poor short-chain PFAS sorption	Potential interferences may significantly impact results due to low reporting limits; PFAS cross-contamination; false positives are common

EPA Method 1621 is a multi-laboratory validated method that estimates the AOF concentration in aqueous samples, including wastewater and landfill leachate. AOF is determined by concentrating organofluorines onto granulated activated carbon (GAC) and removing inorganic fluoride from the GAC, followed by combustion ion chromatography (CIC) analysis to measure fluorine (F) content.

The interpretation of AOF results for wastewater and landfill leachate samples is complicated by two primary factors. First, the shorter chain PFAS sorb less readily to GAC compared to longer chain PFAS,⁴ resulting in potentially low-biased estimates for total PFAS. Second, the GAC will capture non-PFAS organofluorine compounds (e.g., pesticides and pharmaceuticals), leading to potential high biased estimates for total PFAS. Several other potential interferences and considerations, including high chloride concentrations, are also addressed in the method. Additional research is needed to fully understand the limitations of the method and correlation of AOF data with PFAS concentrations.

EPA Method 1633A, also a multi-laboratory validated method, can be used to analyze aqueous, solid, biosolid, and tissue samples for 40 targeted PFAS. However, nontarget PFAS (i.e., compounds not included on the method’s target list) are commonly present in complex samples such as wastewater and landfill leachate. Thus, Method 1633A alone does not provide a complete estimate of total PFAS concentration.

Some laboratories can perform total oxidizable precursor (TOP) assays, which convert PFAS precursor compounds into terminal PFAS that are included among the target analytes in Method 1633A. While TOP analysis also provides an estimate of total PFAS, it still tends to under-report total PFAS concentrations due to the presence of precursors and transformation products not captured by the method.

Method 1633A has addressed variability associated with individual laboratories adapting drinking water methods for solid samples in different ways. However, this method is technically challenging to perform. Method 1633A requires an experienced analyst to address challenges associated with complex matrices like wastewater samples and to appropriately interpret the resulting data for matrix interferences. To support sample analysis, this method also requires experienced sampling staff to minimize cross-contamination and total suspended solids (TSS), which can dramatically influence sample results.

Current PFAS Analytical Methods for Air Emissions

PFAS in industrial emissions are receiving increased regulatory attention due to evidence that atmospheric transport and deposition are contributing to widespread environmental contamination with PFAS. There are currently no federal regulations for PFAS in emissions, so for EPA to regulate PFAS under the U.S. Clean Air Act, PFAS compounds would first need to be designated as hazardous air pollutants (HAPs). In support of this, North Carolina, New Jersey, and New Mexico have each petitioned EPA to list several PFAS (e.g., perfluorooctanoic acid [PFOA], perfluorooctane sulfonic
acid [PFOS], perfluorononanoic acid [PFNA], and GenX chemicals) as HAPs. Additionally, progress toward air emission regulations would require extensive data collection to gain understanding of this problem. Data collection has been limited by the availability of validated test methods and the availability of analytical standards necessary to support analyses.

EPA’s Air Emission Measurement Center (EMC) is working to address these gaps by developing applicable test methods. Other Test Methods (OTMs) are non-regulatory emission measurement methods developed to support ongoing method development and performance testing. They are also used to provide a common “best practice” method to be used by regulators, industry, and the public to sample and analyze for PFAS. The OTM methods are performance-based so that laboratories can modify the methods, assuming they can demonstrate that their analytical approach meets specified performance criteria through method validation.

The methods currently under development by EMC include the following and are summarized in Table 2:

• Other Test Method 45 (OTM-45) Measurement of Selected Per- and Polyfluorinated Alkyl Substances from Stationary Sources, Revision 1, January 14, 2025.⁵
• Other Test Method 50 (OTM-50) Sampling and Analysis of Volatile Fluorinated Compounds from Stationary Sources Using Passivated Stainless-Steel Canisters, Revision 0, January 14, 2025.⁶
• Other Test Method 55 (OTM-55) – initial draft still under development.

Method ID	OTM-45	OTM-50	OTM-55
Status	Draft, Revision 0	Draft, Revision 1	Under development
Purpose	Quantitative analysis for semivolatile and condensable PFAS with the capability to differentiate between particulate-bound and gaseous fractions	Quantitative analysis for targeted volatile fluorinated compounds (VFCs) and degradation products from incomplete destruction (PID)	Quantitative analysis for fluorotelomer alcohols (FTOHs), nonpolar semivolatile fluorinated compounds (SVFCs), and PID
Target PFAS	49 Semivolatile PFAS (polar) listed in method. List is consistent with Method 1633A	30 Volatile PFAS (non-polar) listed in the method. Tentatively identified compounds (TIC) possible	Target list not yet determined. TIC possible.
Collection Media	Complex sample collection train with glass or quartz fiber filters, impingers, and XAD-2 resin traps	Passivated silicon ceramic lined stainless-steel canisters (e.g., Summa). Impingers needed for high moisture and/or high acid gas samples	Similar to OTM-45
Samples	Four sample fractions collected from an isokinetic sampling train	Single sample collected into 6-liter passivated canister	To be determined (TBD)
Analytical Method	LC-MS/MS, based on Methods 533 and 1633	GC-MS with full scan and/or selected ion monitoring (SIM)	GC/MS, TBD
Quantification Technique	Isotope dilution quantification with summation data of sampling train Fractions	Internal standard quantification	TBD
Reporting Limits (estimate)	0.5 to 5.5 ng/m3	0.08 to 0.81 ng/m3	TBD
Quality Control	Robust QC includes instrument standards, spikes, field and laboratory blanks, surrogates, and other QC check standards.	Robust QC includes instrument standards, spikes, field and laboratory blanks, surrogates, and other QC check standards.	TBD
Limitations	Limited to ionic PFAS; may miss neutral or volatile PFAS	Does not capture particle-bound PFAS; canisters unsuitable for some analytes	Method is still evolving
Challenges	Maintaining appropriate probe and filter temperatures, sample preservation, PFAS free sampling materials	CO2 and other non-target interferences	Small sample volume, availability of chemical standards, PFAS free sampling materials

Concluding Thoughts

As concerns over PFAS in waste streams and air emissions continue to grow, sample collection and testing capabilities continue to improve, but not without challenges and limitations. Sample collection and analysis by methods like EPA Method 1633A for solids and liquids and the OTM methods for air represent real progress, but challenges remain with complex or variable matrices, difficult sampling conditions, and changing analytical methodologies.

Getting the right data starts with ensuring the data will be accurate, defensible, and fit for their intended purpose. This starts with understanding your data needs and data quality objectives (DQOs). Once DQOs are established, generating the right data requires proper sample collection and selecting the most appropriate method. That means employing experienced staff for sample collection and selecting a validated analytical approach that matches the sample type and PFAS compounds of interest. It also means applying strong QA/QC practices and taking the time to review and interpret results in their full context.

Improper sample collection procedures or analytical techniques can lead to inaccurate data, which may result in misleading results, inappropriate response actions, and/or inaccurate assessment of risks to health and the environment. The costs associated with these issues also cannot simply be ignored. Continued method development and standardization are essential for producing reliable data, improving consistency across labs, and staying aligned with evolving regulations. To support sound risk management, environmental stewardship, and public confidence, investing in well-established sampling and analytical approaches is necessary, not just for compliance, but for making informed decisions grounded in quality data.

Originally published in EM Magazine November 2025

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References

1. U.S. Environmental Protection Agency, Office of Water. Effluent Guidelines Program Plan 15; U.S. EPA: Washington, DC, 2023.
2. U.S. Environmental Protection Agency, Office of Water. Method 1621 Determination of Adsorbable Organic Fluorine (AOF) in Aqueous Matrices by
   Combustion Ion Chromatography (CIC); U.S. EPA: Washington, DC, 2024.
3. U.S. Environmental Protection Agency, Office of Water. Method 1633, Revision A, Analysis of Per- and Polyfluoroalkyl Substances (PFAS) in Aqueous, Solid,
   Biosolids, and Tissue Samples by LC-MS/MS; U.S. EPA: Washington, DC, 2024.
4. Hansen, M.C.; et al. Sorption of Perfluorinated Compounds from Contaminated Water to Activated Carbon; J. Soils Sediments 2010, 10 (2), 179-185.
5. U.S. Environmental Protection Agency. Other Test Method 45 (OTM-45) Measurement of Selected Per- and Polyfluorinated Alkyl Substances from Stationary
   Sources, Revision 1; U.S. EPA: Washington, DC, January 14, 2025.
6. U.S. Environmental Protection Agency. Other Test Method 50 (OTM-50) Sampling and Analysis of Volatile Fluorinated Compounds from Stationary Sources Using
   Passivated Stainless-Steel Canisters, Revision 0; U.S. EPA: Washington, DC, January 14, 2025.